No periods on the pill

I have been on the mini pill for 6 months now (cerrelle) and only had two periods to begin with. Now I don't get any? Although this is a blessing to not get periods it can still be a pain when your trying to figure out if your pregnant or not. Because I can never tell if I'm late. Is there anyway of knowing when your period is while your on the pill? I just never bleed anymore..